The term “cardboard packaging” usually refers to packaging whereof at least 90 to 98 wt % consists of cellulosic materials. In addition to the layers of cellulosic materials, this type of packaging comprises metal layers or coatings, such as aluminum, or synthetic layers or coatings, associated with the cellulosic materials to form a composite surface material. According to the generally accepted vocabulary, these metal or synthetic coatings make up a “barrier material” isolating the product stored inside the package from the outside environment, for example to prevent oxidation or drying out, or to provide protection from chemical or biological pollutants. The synthetic layers/coatings may also play an essential role in the sealing between two parts of the packaging during the manufacture thereof; in that case, they are generally described as “reactivatable barrier material.”
French patent no. 94 02003, published under no. FR 2 716 408, describes the manufacture of a tubular package of the type described above. The covering structure is formed by a lid cardboard made from a cellulosic material and a safety membrane made from a cellulosic material covered with a barrier material. These two pieces are formed one after the other, in the form of cylindrical basins using a shaping punch through an outer die and engaged in one end of the tubular body. The lateral walls of the two pieces are sealably assembled with the inner wall of the tubular body. The wall of the tubular body is then cut out along a peripheral line situated between the assembly areas of the two pieces, so as to allow the lid cardboard to be opened without tearing the safety membrane.
The drawback of this package is that with wear, after the lid has been opened and the safety membrane has been removed so as to be able to remove a first quantity of the contents, the lid cardboard without protection no long provides enough sealing for the box to maintain the freshness of the unused product for several days or weeks.